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Forms of fasting

Barbara Philipps - 09/02/2024 - 0 comments


Overview of different types of fasting

Fasting is in the nature of both humans and animals. It helped our ancestors survive seasonal and other periods of food scarcity. As it was generally difficult to find enough food to eat at night and in the dark winter months when food supplies ran low, it was customary to fast. Fasting enables the body to draw on its own energy reserves. This was vital when food could not be stored for longer periods of time. Nowadays, however, we have an abundance of food in the regions we live in: It is available around the clock, all year round, and as a result, we have lost the natural rhythm of eating and fasting. That is why we define fasting as giving up food voluntarily for preventive, therapeutic, religious, cultural or other reasons.

When we fast, the body obtains the energy it needs from stored reserves. This causes the metabolism to change so that it burns mainly fat and ketone bodies instead of the glucose absorbed in food. This metabolic change has numerous health benefits: It not only reduces abdominal fat, but also causes overall body weight to drop. The lipid and glucose metabolism improves, inflammation subsides and the organism initiates cleansing processes that eliminate old and damaged cell structures and cells. One of these processes is called autophagy, a kind of endogenous recycling programme, and the other is apoptosis, which brings about programmed cell death. In addition, repair and regeneration processes are triggered at the cellular level, which are then activated as soon as the body is supplied with food again.


Differences between different forms of fasting

Over time, different forms of fasting have evolved. Some restrictive diets are often referred to as “fasting”, but as they do not bring about the desired metabolic change, we will deal with them separately.

One way in which types of fasting differ is their duration, which can range from a few hours to several weeks. Another important factor is frequency, in other words, how often a fast is repeated. Some fasting programmes rule out sources of energy altogether, whereas others – such as the Buchinger Wilhelmi fasting method – allow a minimum intake of nutrients in the form of fasting broth and juice. What form of fasting people choose is also influenced by their reasons for abstaining from food – such as preventive or therapeutic aspects – as well as the decision whether to fast in a specialised clinic or at home.

Fasting as we understand it is characterised by three dimensions: the physical and medical dimension, the spiritual and mental dimension, and the interpersonal dimension. How relevant these different dimensions are depends on where you fast. In the following, we present the most important forms of fasting and nutritional strategies.

Long-term fasting

Long-term fasting is defined as fasting over a period of at least four consecutive days and up to several weeks.

The duration of the fast depends on a person’s individual state of health. Buchinger Wilhelmi has more than 100 years of experience with this form of fasting. The Buchinger Wilhelmi fasting programme is a type of modified long-term fasting that includes a low calorie intake in the form of consommé, organic juices and possibly a little honey.

This supplies the body with 70–250 kcal a day. With modified fasting, an upper limit is recommended in terms of energy intake that corresponds to 25 percent of a person’s individual energy requirements. The upper threshold for a moderately active person of normal weight with an energy requirement of around 2000 kcal per day is therefore 500 kcal per day or lower, depending on the person’s physical constitution. Solid foods are consciously omitted to prevent feelings of hunger being triggered by chewing. The fasting programme offered by Buchinger Wilhelmi prescribes evacuating the bowels at the beginning of the fast and regularly cleansing them during the fast, as well as daily liver wraps.

Medical Supervision

Long-term fasting should ideally be done under medical supervision in a fasting clinic. This is often referred to as therapeutic fasting. Dr. Otto Buchinger, the originator of therapeutic fasting and founder of the Buchinger Wilhelmi clinics, developed a multidisciplinary fasting regime that has been continuously developed right up to the present day by the following generations of his family. Medical and therapeutic care, inspiration, and being part of a community are essential for the success of fasting. People who want to change their lifestyle in the long term also benefit from nutritional advice, physiotherapy and massages, fitness training, psychotherapy and the inspiring, health-promoting environment of the Buchinger Wilhelmi clinics.

Scientific findings

The Buchinger Wilhelmi fasting programme is scientifically documented. Numerous studies have been carried out that prove the preventive and therapeutic effects of fasting, such as:

  • reducing weight and abdominal circumference,
  • normalising the lipid and glucose parameters in the blood,
  • increasing the antioxidative capacity and inhibiting inflammatory processes,
  • modulating the blood pressure in a positive way, and
  • reducing and regenerating a fatty liver.

On our YouTube channel you will find numerous videos in which the effects of fasting are explained in detail by our fasting experts. You will also find tips on how to prepare and carry out fasting cures and how to break your fast.

Other forms of long-term fasting

Other forms of fasting that can also be considered long-term fasting because they generally last at least several days include juice fasting, a whey cure, gruel fasting and water fasting.

🍹Juice fasting

As the name suggests, juice fasting involves drinking only fruit and/or vegetable juice (usually freshly pressed). Attention should be paid to the calorie and sugar content. Fruit juice contains a lot of sugar (fructose and glucose), and can easily exceed the upper limit for energy intake that is compatible with fasting, preventing the body from changing to the fasting metabolism. For this reason, the term “juice fasting” is often misleading, because if it does not comply with the recommended upper limit, then it is a diet. We have created a guide article on the subject of “juice fasting”: Therefore no juice fasting.

🥛 Whey cure

In a whey cure, water, tea and juice are supplemented with whey, which can help calm a sensitive stomach. Again, there is the risk that the body might be prevented from switching to the fasting metabolism – this time due to an excessive protein supply from whey. Latest studies show that occasionally restricting protein intake is good for your health. Even cutting down on individual amino acids, which are the basic component of proteins, can have a similar effect to fasting. For this reason, taking protein supplements, for example in the form of whey, should be carefully considered and applied carefully.

💧 Water fasting

Water fasting is the most radical form of fasting and is limited to water only without any added calories or nutrients. Water fasting should always be done under medical supervision, as it places much more strain on the body than modified fasting. The therapeutic effects may set in more quickly and can be more intense, but the transition to total fasting is often difficult and not always well tolerated. People on a water fast are often instructed to avoid doing too much exercise. However, this contradicts the approach followed by Buchinger Wilhelmi, which sees physical activity as an important part of the fasting programme.

🥣Gruel fasting

Gruel fasting involves eating a thin gruel made from oats, rice or linseed. We consider it to be an extension of modified fasting, but not a fasting category in its own right.

Short-term fasting

Short-term fasting means fasting over a period of two to three days at the most. Intermittent fasting is also included in this category.

Daily intermittent fasting

One of the simplest forms of intermittent fasting is limiting one’s daily food intake to a certain time window. This means taking a break of 10 to 16 hours between meals, during which no solid food or calorific drinks such as sweetened tea, milky coffee, soft drinks or juice are permitted. For the remaining time, food consumption is not restricted.

This model is relatively easy to follow by simply missing out either breakfast or dinner or taking them later or earlier. Alternating phases of eating and fasting is very similar to the natural eating habits of our ancestors. Individual preferences and social aspects, such as family meals, can be taken into account when planning mealtimes. Intermittent fasting is also ideal as a gentle introduction to fasting. However, it is not yet clear how long the ideal break between meals should be to achieve the best results.

Fasting during Ramadan – the Muslim fasting month – is also a form of intermittent fasting. During this period, food may only be consumed at night, or to be exact, between sunset and sunrise. Some Muslims also give up drinking liquids during the day. However, this is not recommended from a health perspective.

16:8 method

One of the most popular forms of intermittent fasting is the 16:8 method, in which you fast for 16 hours and restrict food intake to eight hours in-between.

Warrior Diet

A stricter version is the so-called Warrior Diet. In this case, the time window within which you are allowed to eat is restricted to four hours. This diet is based on the lifestyle of Stone Age people who only ate once a day after a successful hunt.

OMAD (One Meal A Day) diet

The most extreme version of intermittent fasting is the so-called OMAD (One Meal A Day) diet in which food intake is limited to one hour a day. Due to the long breaks between meals, this type of fasting is not particularly practicable in the long term. Restricting your overall food intake to one large meal a day can cause feelings of lethargy and – if the meal is taken in the evening – lead to sleeping problems.

Periodic fasting

Alternate-day fasting means fasting completely or in a modified form every second day. On the other days there are no restrictions at all. This strict rhythm requires discipline and limits your ability to participate in social activities. An alternative to this is fasting on individual days each week. The 5:2 method involves fasting or restricting calorie intake – usually to max. 800 kcal/day – on either two consecutive days or two separate days of the week. However, this form of fasting does not achieve the beneficial metabolic effects of long-term fasting. The method is easier to maintain if you fast on two separate days of the week. A very strict form of intermittent fasting is omitting not just food, but also liquids on individual days of the week. This often has a religious background and is not recommended for health reasons.

Fasting mimicking diet

The fasting mimicking diet is a relatively new trend. It is a calorie-reduced diet that has a similar metabolic effect to fasting and restricts energy intake to 600–1200 kcal per day. The diet consists of plant-based meals that are low in carbohydrates and proteins but relatively high in fats. Thanks to this combination of nutrients, the body can switch to the fasting metabolism, called ketosis. Solid foods are allowed but they should contain as little refined sugar and dietary fibre as possible. The fasting mimicking diet is usually carried out for 3–7 days.

Buchinger Wilhelmi’s FASTING BOX is a low-calorie, ketogenic five-day reset programme that is done at home and can be easily integrated into day-to-day life.

The User Guide included in each FASTING BOX provides detailed information on the course of the programme. Users also have access to an app with supportive video messages, tips and other useful information.

There is also an online community where people can swap notes with others and ask experts questions.

Who should not fast, or only after consulting a doctor?

People with a metabolic disorder, any other chronic illness or acute cancer as well as the elderly should get medical advice before fasting and only fast under medical supervision. Fasting is generally not suitable for women who are pregnant or breastfeeding, for children and adolescents, as well as for people who are underweight or have an eating disorder.

Special diets

Some diets use the word “fasting” in their name, although they are not proper fasting, as they do not result in a metabolic change. One of these is fruit fasting.

🍏 Fruit fasting

Fruit fasting involves eating three to five portions of fruit every day, as well as vegetables and nuts. It is therefore a diet that is rich in vitamins, minerals and fibre. Stricter variants limit food intake to a few or even just one kind of fruit, e.g. apples, or restrict the amount of fruit that can be eaten each day. This diet is easy to follow and does not need a great deal of preparation. In addition, thanks to the special choice of food, it can help relieve the immune system.

Another model is a pure fruit and vegetable diet without calorie reduction. However, we advise against such one-sided nutrition strategies.

🚫 Continuous calorie restriction

In this diet, the amount of energy supplied daily with food is reduced by around 30 percent of the daily requirements. People can decide for themselves when to eat. Studies have demonstrated that this diet has numerous benefits, such as an anti-inflammatory effect or a longer lifespan in animal models. However, it is often not easy to follow in day-to-day life. In the long term, people on this diet risk becoming underweight.

🥑 Low-carb diets

Many diets involve reducing the intake of certain nutritional components, such as carbohydrates, protein or fat. If high-carbohydrate food like bread, pasta, potatoes and rice are taken off the menu and replaced with products with a high protein and fat content, this is called a low-carb or ketogenic diet. Restricting the intake of carbohydrates causes the insulin and blood sugar levels to drop, causing the body to burn fat. Not all low-carb diets are automatically ketogenic. A ketogenic diet is a form of nutrition with a high fat content, an adequate protein content, and a highly restricted carbohydrate intake. Similar to fasting, this activates cellular signal paths that are largely responsible for the positive effects of this nutritional strategy. Implementing a ketogenic diet requires discipline and is generally not recommendable as a long-term form of nutrition.

🌿 Low-protein diets

Limiting the daily intake of protein also leads to a modulation of the metabolism, resulting in improved blood sugar and insulin levels. These positive effects can also be achieved by restricting the supply of individual amino acids, such as methionine. A low-protein diet can be done with plant-based nutrition. Animal products, on the other hand, are mostly rich in protein. For example, the residents of the Japanese island Okinawa are known to live particularly long, partly because they live on a low-protein diet.

🥦 Low-fat diets

Low-fat diets are based on limiting the amount of fat eaten, which is often too high in Western countries and causes obesity. At 9 kcal per gramme, fat is the macronutrient with the highest energy content. Carbohydrates and proteins supply half as much energy with 4 kcal per gramme. A low-fat diet therefore often means eating more food with a low energy supply. This makes it possible to consume larger meals and/or more dietary fibre, which makes you feel fuller than eating a small amount of high-fat food with the same amount of calories. It is important to make sure you have a sufficient supply of essential fatty acids, for example, from linseed and walnut oil, avocados and nuts. Animal fats, such as oily sea fish, should only be consumed in moderation and chosen carefully. A low-fat diet can be effective for weight loss and is also recommended for certain health conditions from a medical point of view.

Our recommendations

Fasting has numerous preventive and therapeutic effects and activates the body’s self-healing powers. It can be an important component for ensuring a long, healthy life.

  • Basically, we recommend a combination of different forms of fasting and nutritional strategies
  • If you fast once a year for a longer period, you can supplement this during the rest of the year with intermittent fasting, for example, and/or a reset with our FASTING BOX
  • Before choosing a form of fasting or a certain diet, it is important to get in-depth information and medical advice
  • Regardless of this, it is essential that you eat a diet that is as balanced as possible with plant-based ingredients. Seasonal, fairly produced food from local organic farms that is only minimally processed is the best choice. Learn more

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